Safety band brake for high-speed tools



Aug. 30, 1949. SULLY SAFETY BAND BRAKE FOR HIGH-SPEED TOOLS 2 Sheets-Sheet 1 Filed Jan. 21, 1943 TTORNE INVENTQR Jbim BY A z J. sum 2,480,343

' Filed Jan; 21,- 1943 SAFETY BAN BRAKE ,Fon HIGH-SPEED TOOLS v 2 Shets-Sheet 2 ATTORNEY Patented Aug. 30, 1949 SAFETY BAND BRA KE Fen HIGH-SPEED TOOLS .iohn Sully, Joliet, 1H,, assignor to American; Gar:

and Foundry Company, New York, N. Y a corporation of New Jersey Application January 21, 1943, Serial No. 473,107

Claims.v

Thisv invention relates to electrically driven portable tools in general and in particular to high speed electrically driven tools, reamers and such like.

Recently, in order to make drills, reamers, etc., lighter and more easily handled, the trend has been toward extremely high speed motorsv for driving tools. In addition better steels and coatin'g alloys have been developed permitting. higher cutting speeds. The use of high speed tools is always dangerous for if a workmans clothing becomes entangled in the tool an injury is apt to occur almost immediately. It is, therefore, imperative that the tool be stopped immediately upon an emergency arising. It is an object, therefore, of the present invention to provide a device for stopping high speed tools immediately upon breaking of the current supply to the driving motor.

A further object of the invention is the provision of a compact and light weight braking arrangement which can be applied to existing high speed tools with a minimum of modification,

A still further object of the invention is the provision of a brake for a a high speed tool, which brake is held on by the operator during use of" the tool and immediately applied when for any reason the operators grip on the tool is relaxed.

These and other-objects of the invention will be apparent to persons skilled in the art from a study of the following description and accompanying drawings, in which: I

Figure 1 is a sectional view of the safety attachment and showing the attachment applied to a high speed tool;

Fig. 2 is a plan view of the attachment with the top cover plate removed; 7

Fig. 3 is an end View of a portion of the attachment and better disclosing the means by which it may be connected to the tool switch, and

Fig. 4 is a sectional view taken substantially on line 4- of 2 but with the cover plate in place.

Referring now to the drawings in detail, it will beseen that the attachment A in general has been illustrated in full lines and is shown as applied to a high speed tool Bindicated in general by line and dash (Fig. 1). The high speed tool as indicated is provided with handles 2, one of which encloses the switch and switch tool mechanism for the motor, the armature of which is indicated at 3. The switch tool mechanism includes a lever part l connected by suitable linkage to the switch part 6. As shown in Fig. l the lever part 4 is in the position which it occupies when gripped 2 by the operator in; other words, the switch is in the on -position: and" current would; be fed, to the electric motor to drive the same. Int-his cm position the switch, control mechanism come presses a spring 8' or sufiicientstrengtn to immedia ately turn the switch part 6 to off-position when the operators grip is relaxed permitting hand-1e ll to fly upwardly. This type of control is more or less conventional but it will be seen that no cone trol is given preventing coasting of: the. motor and connected parts after the current is turned off.

In order to prevent coasting of the motor armature 3 after the current has. been turned off of the motor, the safety attachment A,previously re: ferred to; is applied as a unit to the tool. The safety attachment, as clearly shown, consists. of a base plate ill to which is welded or otherwise secured sides l2. The base plate. is provided with openings for reception of bolts I4 by means of which it may be secured to the frame of the tool B. An opening is also provided in the base plate through which a short shaft 86 extends, which shaft is adapted to be secured to a driven shaft E8 of the high speed tool. Thisdriven shaft is preferably the armature shaft of the tool. As

shown, the short shaft 16 has keyed thereto as at 2i] a brake drum 22 held in place by nut 24. The brake drum is adapted to be gripped by a brake lining 26 fastened to a brake band 28 which in turn is fastened to short operating arms 30;

One of the arms 30 has secured thereto a short piece of pipe 32 adapted to engage an anchor pin 34 fastened to the base plate. A strap 36 is also secured to the short piece of pipe and provided with an opening to receive the hooked end 38 of a spring 49, the opposite end of which is hooked into an opening 42 of the other brake operating arm. This spring is placed under tension and always tends to pullthe operating arms together squeezing the brake lining against the brake drum.

The moving operating arm 39 is adapted to rub against a plate'or wedge block is fastened to the base plate by any suitable means such as machine position. In this way riding of the released brake I band on the drum is prevented.

In orderto' counteract the spring tension and provide control over the operation of the brake band, a cam finger is termed on the upper end of an operating shaft 52 extending through the base plate and through a part of the tool casing to a point adjacent the switch part 6 previously referred to. The lower end of the operating shaft has secured thereto an arm 54, to the free end of which is attached as by bolt 56 a link 58. The free end of the link has attached thereto as by bolt 60 a bracket part 62 which can be welded or otherwise secured to the switch part 6. Wear of the brake lining 26 is compensated for by means of an adjusting bolt having a. large square head 10 and a shank 12 having threaded engagement with the brake operating arm and locked in position by lock nut '74. Thecasing housing the brake and operating parts is completed by means of the top cover plate 16 held in place by the bolts l4 and preferably provided with a handle part 18 permitting ready carrying of the tool. This handle part can in most cases be the original handle part of the tool.

From the preceding description it will be seen that the safety brake can be built up as a unit and applied to existing tools without any material or major change being necessary in the tool, nor will the operation of the tool be modified insofar as the operator is concerned. The operation of the safety brake is as follows, assuming the parts to be in the position shown in the figures, that is, with the lever 4 held down by the operator against springs 8 and id and with the switch part 6 in position to feed current to the motor. With the parts in this position the brake is released as shown in Fig. 2, that is, the cam finger 50 bears against the adjusting plate 10 forcing the operating arms apart and causing the one arm to slide along the wedge plate 44 and move toward the brake drum, thereby wholly releasing the brake band from the brake drum. If for any reason the operator relaxes his grip on the handle, the lever 4 will fiy up due to the energy stored in springs 8 and 49. This will immediately shift the switch part 6 causing the operating shaft 52 to be rotated in a clock wise direction as viewed in Fig. 2. Such a rotation allows the operating arms to approach each other under the urge of the spring 40. Approach of the operating arms 33 will cause the brake lining 26 to grip the brake drum 22 and since the rotation of the brake drum is in a counterclockwise direction as viewed in Fig. 2, the band tends to wrap and tightly grips the brake drum bringing it to an almost immediate stop yet without the shock which would be occasioned by a positive grip. It will thus be seen that no conscious effort is necessary on the part of the op-' erator to stop the tool operation and such a condition is necessary to prevent accidents.

Whil the invention has been described more or less in detail, it will be obvious to persons skilled in the art that various modifications and rearrangements of parts may be made and all such modifications and rearrangements of parts are contemplated as will fall within the scope of the appended claims defining my invention.

What is claimed is:

1. As an article of manufacture for use with a portable tool controlled by a switch, a safety brake comprising, a housing adapted to be secured to the tool, a brake drum in the housing adapted to be connected to a rotating shaft of the tool, a brake band located in the housing and substantially encircling said brake drum, means anchoring one end of said brake band in the housing, a guide plate secured to the housing and adapted to be engaged by the other end of said 4 brake band as said brake band is moved toward released position, said guide plate being so arranged as to move the free end of said brake band toward the brake drum during releasing movement of said band, resilient means constantly urging said brake band toward gripping engagement with said brake drum, a cam finger engaging a part of said band and cooperating with said guide plate to hold the brake band in released position and operating means for said cam finger.

2. A safety brake for a rotatable brake drum, said brake comprising a brake band anchored at one end and substantially encircling the brake drum, a guide plate engageable by the other end of said brake band and so arranged as to shift said other end of the band toward said brake drum during release of the brake, means constantly urging said brake band toward gripping engagement with said brake drum, means hearing on a part of said brake band and together with said guide plate normally preventing said gripping engagement, and operating means controlling said last named means to permit said gripping engagement.

3. A safety brake for a rotatable brake drum comprising, a substantially circular brake band anchored at one end and free at the other end, means constantly urging said brake band toward gripping engagement with the brake drum, and means counteracting said first named means and normally holding said brake band to its substantially circular form but out of engagement with the brake drum, said last named means including a wedge plate disposed in the path of movement of said free end of the brake band and so arranged as to cause said free end to shift toward the brake drum during release of the brake band.

4. A safety brake for high speed tools having a driving motor, said safety brake including a brake drum connected to the motor armature and rotatable thereby, a brake band anchored at one end and substantially encircling the brake drum, a guide plate engageable by the free end of said brake band and so arranged as to shift said free end of the brake band toward said brake drum when the brake is released, a spring constantly urging said brake band toward gripping engagement with said brake drum, a cam finger bearing on a part of said brake band and normally preventing said gripping engagement, and operating means controlling said cam finger to permit said gripping engagement.

5. A safety brake for high speed tools having a controlled driving motor, said safety brake ineluding a brake drum connected to the motor and rotatable thereby, a brake band substantiall encircling the brake drum, projecting ends attached to said brake band, anchor means for one of said projecting ends, a. guide plate slidably engaged by the other projecting end and so arranged as to move said other end toward the brake drum when the brake band is in released position, a spring constantly urging said ends toward each other whereby said band may be brought into gripping engagement with said brake drum, a cam finger interposed between said pro jecting ends, said guide plate and cam finger normally preventing said gripping engagement of the band and drum, and operating means for said cam finger whereby said cam finger may be moved to permit said gripping engagement.

JOHN SULLY.

(References on following page) Number REFERENCES CITED 1,798,504 The following references are of record in the 1942 3525 file of this patent: 1,969,528 5 2,125,543 UNITED STATES PATENTS 2,164300 Number Name Date 2 233 793 731,646 Wilson et al June 23, 1903 2,271,247 746,057 Knowles Jan. 11, 1910 1,216,424 Edwards Feb. 20, 1917 0 1,555,987 Kimball Oct. 6, 19 Number 1,646,539 Johnson Oct. 25, 1927' 331,598

Name Date Straub et a1 Mar. 31, 1931 Meunier J an. 9, 1934 Schwarzhaupt Aug. 7, 1934 Chandler Aug. 2, 1938 Smith, Jr. June 2'7, 1939 Robins Mar. 4, 1941 Brown et a1 Jan. 27, 1942 FOREIGN PATENTS Country Date France Aug. 1, 1903 

